This invention relates to an apparatus for facilitating the connection of tubulars using a top drive and is more particularly, but not exclusively, intended for facilitating the connection of a section or stand of casing to a string of casing.
In the construction of oil or gas wells it is usually necessary to line the borehole with a string of tubulars known as casing. Because of the length of the casing required, sections or stands of say two sections of casing are progressively added to the string as it is lowered into the well from a drilling platform. In particular, when it is desired to add a section or stand of casing the string is usually restrained from falling into the well by applying the slips of a spider located in the floor of the drilling platform. The new section or stand of casing is then moved from a rack to the well centre above the spider. The threaded pin of the section or stand of casing to be connected is then located over the threaded box of the casing in the well and the connection is made up by rotation therebetween. An elevator is then connected to the top of the new section or stand and the whole casing string lifted slightly to enable the slips of the spider to be released. The whole casing string is then lowered until the top of the section is adjacent the spider whereupon the slips of the spider are re-applied, the elevator disconnected and the process repeated.
It is common practice to use a power tong to torque the connection up to a predetermined torque in order to make the connection. The power tong is located on the platform, either on rails, or hung from a derrick on a chain. However, it has recently been proposed to use a top drive for making such connection. A xe2x80x9ctop drivexe2x80x9d is a top driven rotational system substantially used for drilling purposes, assigned to the drawworks at a higher level than the elevator, as is previously known.
Because of the high costs associated with the construction of oil and gas wells time is critical and it has been observed by the applicants that the time to connect a tubular to a top drive using existing equipment could be reduced.
According to a first aspect of the present invention, there is provided a tool that will facilitate the running of a casing string into a well bore, comprising:
(a) a grapple machined with both horizontal and vertical xe2x80x9cwhickersxe2x80x9d or serrated teeth for gripping the tubular innerwall, complete with a wedge locking mechanism;
(b) a hydraulic mechanism for locking and unlocking the grapple and wedge lock mechanism, thus providing a xe2x80x9cpositive lockxe2x80x9d situation;
(c) a compression spring provided within the hydraulic lock piston applying positive locking to the grapple and wedge lock arrangement;
(d) a check valve that will prevent mud spillage during casing fillup and circulation;
(e) an inflatable or pressure operated pack-off that will permit fillup or casing circulation to take place at any given time once installed within the casing string; and
(f) a connection for connecting the device to the rig based equipment for running casing into a well bore.
According to a second aspect of the present invention there is provided apparatus (201) for running tubulars (213) into a borehole, said apparatus comprising a body (202) provided with a wedge lock assembly (212) and a hydraulically operable grapple (210) to mechanically grip the inside wall of a tubular (213) to be run into, or withdrawn from, the borehole, said grapple incorporating positive locking means to prevent inadvertent release of said grapple, said body further comprising means (214) to prevent spillage of drilling fluid when the body is withdrawn from the tubular, a sealing packer (215) for engagement with the tubular to permit fluid to be circulated within the tubular, and a stabbing guide (216), characterised in that said grapple (210) comprises horizontally and/or vertically aligned whickers or serrated machined teeth and said stabbing guide is a rubber stabbing guide to prevent damage when entering a tubular.
In use, such an apparatus may be connected to a top-drive unit via a threaded connection, or to a kelly driven rig via a pump joint latched into an elevator. Both systems have available a means of connecting up to a circulating system that will permit the casing to be filled or circulated at any time during the running operation.
Casing is normally run by picking up a joint at a time, utilising single pickup elevators to bring the joint into the derrick and connect it to the previously run joint, whether it be by threaded connection or xe2x80x9cmechanical latching or lockingxe2x80x9d. The two joints are either screwed or locked together and then lowered into the well bore using elevators.
With heavy casing strings it is required that very large elevators are used to be able to handle the load. This often means that the top of the casing joint must be set 8-10 feet above the rig floor to permit disengagement to take place. Scaffolding is often required for the rig crews to be able to stab or connect the next joint to the string. It is also normal to either utilise a separate pack-off assembly, or a fillup hose that must be installed by the rig crew after it has been lowered and set in the slips.
Preferred embodiments of the present invention will permit the casing to be picked up by single pickup elevators, connected either by rotation or mechanical latch, and then the casing running tool to be xe2x80x9cstabbedxe2x80x9d into the bore of the top joint without damage, due to the rubber bull-nose guide. When the tool is at the correct depth of penetration within the casing bore, the hydraulic piston is actuated to drive the grapple down onto the wedge lock and secure the grapple to the casing wall. As the casing string is lifted, the wedge-lock continues to drive into the grapple bore, providing an ever increasing wedge lock. The compression spring installed within the hydraulic piston provides a xe2x80x9cpositive-lockxe2x80x9d or failsafe should the hydraulic system fail for any reason.
When the apparatus is engaged, it is then possible to push, pull, or even rotate the casing string. A seal ring assembly is required to rotate the casing string, to permit constant control of the hydraulic actuating piston to be maintained.
Preferred embodiments of the apparatus are equipped with a through-bore to permit casing fillup and circulation to take place at any time. There may also be provided a pack-off that can be either inflatable or flow pressure operated.
The present invention also provides a top drive having an apparatus in accordance with the present invention attached thereto.